.TH std::ostrstream::ostrstream 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::ostrstream::ostrstream \- std::ostrstream::ostrstream

.SH Synopsis
   ostrstream();                                              \fB(1)\fP (deprecated in C++98)
                                                                  (removed in C++26)
   ostrstream( char* s, int n, std::ios_base::openmode mode = \fB(2)\fP (deprecated in C++98)
   std::ios_base::out );                                          (removed in C++26)

   Constructs new output strstream and its underlying std::strstreambuf.

   1) Default-constructs the underlying std::strstreambuf, which creates a dynamically
   growing buffer, and initializes the base class with the address of the strstreambuf
   member.
   2) Initialized the base class with the address of the underlying std::strstreambuf
   member, which is initialized in one of the two possible ways, both of which write to
   user-provided fixed-size array:
   a) if the app bit is not set in mode, constructs the buffer by calling
   strstreambuf(s, n, s). The behavior is undefined if there are less than n elements
   in the array whose first element is pointed to by s
   b) if the app bit is set in mode, constructs the buffer by calling strstreambuf(s,
   n, s + std::strlen(s)). The behavior is undefined if there are less than n elements
   in the array whose first element is pointed to by s or if the array does not contain
   a valid null-terminated character sequence.

.SH Parameters

   s    - char array to use as the output buffer
   n    - size of the array to be used as the output buffer
          specifies stream open mode. It is a bitmask type, the following constants are
          defined (although only app is used):

          Constant          Explanation
          app               seek to the end of stream before each write
   mode - binary            open in binary mode
          in                open for reading
          out               open for writing
          trunc             discard the contents of the stream when opening
          ate               seek to the end of stream immediately after open
          noreplace (C++23) open in exclusive mode

.SH Example


// Run this code

 #include <iostream>
 #include <strstream>

 int main()
 {
     std::ostrstream s1; // dynamic buffer
     s1 << 1 << ' ' << 3.14 << " example\\n" << std::ends;
     std::cout << s1.str();
     s1.freeze(false);

     char arr[15] = "Hello";

     std::ostrstream s2(arr, sizeof arr, std::ios_base::app);
     s2 << ", world!" << std::ends;
     std::cout << s2.str() << '\\n';
     std::cout << arr << '\\n'; // streams use the provided arrays
 }

.SH Output:

 1 3.14 example
 Hello, world!
 Hello, world!

.SH See also

   constructor   constructs a strstreambuf object
                 \fI(public member function of std::strstreambuf)\fP
   constructor   constructs an istrstream object, optionally allocating the buffer
                 \fI(public member function of std::istrstream)\fP
   constructor   constructs a strstream object, optionally allocating the buffer
                 \fI(public member function of std::strstream)\fP
